YUSOSEN!

1 May 1936:
Kobe. Laid down as a 9,997-ton merchant tanker by Kawasaki for Iino Shoji K.K.
31 October 1936:
Launched and named TOHO MARU. [1]
24 December 1936:
Completed and registered in the port of Maizuru.
1936:
Completes three short voyages under charter to the IJN.
1937:
Completes nine voyages; five under charter to the IJN, two for Chosen Sekiyu oil companies, one for Mitsui Bussan and one for Nippon Sekiyu.
1938:
Completes nine voyages; eight under charter to the IJN and one for Chosen Sekiyu.
1939:
Completes 14 voyages; 11 under charter to the IJN, two for Chosen Sekiyu and one for Sekiyu Kyohan.
1940:
Completes 11 voyages; seven for the IJN, one for Mitsui Bussan, two for Chosen Sekiyu and one for Nippon Sekiyu.
1941:
Completes five voyages; all for Toa Sekiyu Kyokai.
13 March 1941:
The owners' name is restyled as Iino Kaiun K.K.
20 August 1941:
TOHO MARU is requisitioned by the IJN. Registered as a Converted Transport (Oil supply) in the Yokosuka Naval District.
20 September 1941:
Captain (Rear Admiral, posthumously) Niimi Kazutaka (40)(former CO of TAMA) is posted as the Commanding Officer.
24 September 1941:
Yokohama. Begins conversion to a Navy Replenishment oiler at Mitsubishi Zosen.
3 October 1941:
The conversion is completed.
27-28 October 1941:
The Chief of Staff 1st Air Fleet, Rear Admiral (later Vice Admiral) Kusaka Ryunosuke (41)(former CO of AKAGI) arranges for oilers TOHO and SHINKOKU MARUs to join the 1st Air Fleet by about 10 November. In the meantime, the two oilers are equipped for refueling at sea. The equipment includes special fenders and lines.
18 November 1941: The Hawaii Operation:
Departs Saeki. Seven oilers are assigned to the Hawaii Operation, but the IJN’s practical experience in refueling at sea is almost nil. Earlier in the month, three refueling exercises were held in Sukumo Bay and the Ariake Sea. Now, while enroute to the Kuriles, all units in the carrier formation are refueled ten times.
26 November 1941:
Etorofu Island, Kuriles. TOHO MARU departs Hitokappu Bay with Captain (Rear Admiral posthumously)Niimi Kazutaka's (40) Supply Group No. 2's oiler TOEI MARU and Captain Ota Masanao's (39) Supply Group No. 1's oilers KYOKUTO, KOKUYO, KENYO, NIPPON and SHINKOKU MARUs. Provides fuel for Vice Admiral (Admiral, posthumously) Nagumo Chuichi's (36) Carrier Striking Force ("Kido Butai") CarDiv 1's AKAGI, KAGA, CarDiv 2's HIRYU and SORYU, CarDiv 5's SHOKAKU and ZUIKAKU and the Support Force.
The Support Force consists of Vice Admiral Mikawa Gunichi's (38) BatDiv 3/1's HIEI and KIRISHIMA, Rear Admiral (later Vice Admiral) Abe Hiroaki's (39) CruDiv 8's TONE, CHIKUMA and Rear Admiral (later Vice Admiral) Omori Sentaro's (41) DesRon 1's light cruiser ABUKUMA and DesDiv 17's ISOKAZE, URAKAZE, TANIKAZE and HAMAKAZE, DesDiv 18's ARARE, KASUMI, KAGERO and SHIRANUHI and CarDiv 5's AKIGUMO and Captain (later Rear Admiral) Konishi Kaname's (44) Midway Bombardment Unit's DesDiv 7's SAZANAMI and USHIO.
Nagumo's orders from Admiral (Fleet Admiral, posthumously) Yamamoto Isoroku, (32) CINC, Combined Fleet, are that if refueling proves impossible in the stormy winter waters of the Northern Pacific, Nagumo is to detach AGAKI, SORYU and HIRYU and his destroyers and make the attack with only KAGA, SHOKAKU and ZUIKAKU that need no refueling.

4 December 1941: [2]
TOHO MARU refuels the destroyer AKIGUMO with 95-tons of fuel.
5 December 1941: [2]
600 miles N of Oahu, Hawaii. At about 1130, after fleet refueling is completed, the 2nd Supply Group's oilers TOHO, NIPPON and TOEI MARUs and destroyer ARARE are detached from the Striking Force and turn towards a designated rendezvous point with the carriers for the retrurn trip to Japan.
6 December 1941: [2]
400 miles N of Oahu, Hawaii. At 0810, after refueling the Carrier Force, the 1st Supply Group's oilers SHINKOKU, KENYO, KOKUYO and KYOKUTO MARUs and destroyer KASUMI are detached and turn towards a designated rendezvous point with the carriers for the retrurn trip to Japan. The Striking Force increases speed to 24 knots and proceeds to Hawaiian waters to launch the attack.
Vice Admiral Nagumo dispatches ABUKUMA and DesDiv 17's TANIKAZE to Supply Group No. 1 at the rendezvous point following final refueling before the attack. At about 2100, the two warships reach the oilers, refuel and return with the oilers to the First Air Fleet.
7 December 1941: [2] Operation "Z" - The Attack on Pearl Harbor:
At 0618, the Carrier Striking Force launches attacks that later sink battleships USS ARIZONA (BB-39), USS OKLAHOMA (BB-37) and USS CALIFORNIA (BB-44) and damage USS NEVADA (BB-36), USS PENNSLYVANIA (BB-38), USS TENNESSEE (BB-43), USS MARYLAND (BB-46), USS WEST VIRGINIA (BB-49) and other smaller ships. 2,335 American servicemen die in the attack, most on ARIZONA. After recovering all but 29 of its aircraft lost in the attack, the Striking Force departs Hawaiian waters NNW towards Japan.
21 December 1941:
SSW of the Bonin Islands. The 2nd Supply Group's oilers TOHO, NIPPON and TOEI MARUs rendezvous with, and refuel, the Striking Force. That same day, seven destroyers of DesDiv 21 and DesDiv 27 from Tokoyama rendezvous with the 1st Air Fleet to provide additional ASW protection.
23 December 1941:
Arrives at Hashirajima.
27 December 1941:
Arrives at Kure.
12 January 1942:
Departs Hiro.
23 January 1942:
Arrives at Saiki, steams to Tokuyama and Kure and then Truk.
20 February 1942: Operation “SR” – The Invasions of Lae and Salamaua, New Guinea:
Departs Truk. Later, provides refueling for CruDiv 6's AOBA, KINUGASA, FURUTAKA and KAKO and CruDiv 18's TENRYU and TATSUTA covering forces.
1 March 1942:
Arrives at Yokosuka.
7 March 1942:
Departs Yokosuka.
1 April 1942: Operation "C "– The Raids in the Indian Ocean:
Vice Admiral Ozawa Jisaburo's (37) (former CO of HARUNA) Second Expeditionary Fleet conducts raids against merchant shipping in the Bay of Bengal with CruDiv 4's CHOKAI, CruDiv 7's SUZUYA, KUMANO, MIKUMA and MOGAMI, CarDiv 4's light carrier RYUJO and SubRon 5's light cruiser YURA and destroyers AYANAMI, YUGIRI, ASAGIRI and SHIOKAZE.
10 April 1942:
Provides refueling support for Ozawa's forces returning from operations in the Indian Ocean.
1 May 1942: Operation "MO" - The Invasions of Tulagi and Port Moresby:
Sorties from Truk in support of the invasion of Tulagi with Vice Admiral (promoted that day/Admiral, posthumously) Takagi Takeo's (39)(former CO of MUTSU) Carrier Striking Force's CarDiv 5's ZUIKAKU and SHOKAKU, CruDiv 5's MYOKO and HAGURO, DesDiv 27's ARIAKE, YUGURE, SHIGURE, SHIRATSUYU and DesDiv 8's USHIO and AKEBONO.
4 May 1942:
In the morning, TOHO MARU refuels Takagi's ships.
6 May 1942:
In the afternoon, Takagi orders his Carrier Striking Force to turn northward. At slow speed, TOHO MARU refuels Rear Admiral (later Vice Admiral) Hara Chuichi's (39)(former CO of TATSUTA) CarDiv 5's ZUIKAKU and SHOKAKU and Takagi's other ships.
7 May 1942: The Battle of the Coral Sea:
In the predawn hours, Rear Admiral Hara persuades Takagi to break off refueling and reverse course southwards. At 0700, Hara launches recon aircraft to find the Americans. At 0900, a plane spots a "carrier and heavy cruiser", actually oiler USS NEOSHO (AO-23) and destroyer USS SIMS (DD-409). Takagi's carriers then launch three waves of attack planes that sink USS SIMS and so damage NEOSHO that she has to be scuttled four days later.
At 1135, SBD dive-bombers and TBD torpedo-bombers from Rear Admiral (later Admiral) Frank Jack Fletcher’s (USNA ’06) Task Force 17's USS YORKTOWN (CV-5) and USS LEXINGTON (CV-2) find and sink Rear Admiral (Vice Admiral, posthumously) Goto Aritomo’s (38) light carrier SHOHO off Misima Island.
8 May 1942:
At 1030, YORKTOWN's SBDs find the Japanese carriers. At 1057, YORKTOWN's TBD torpedo-bombers attack SHOKAKU unsuccessfully, but her SDBs damage SHOKAKU and force her retirement. The ZUIKAKU’s air group suffers heavy losses.
Rear Admiral Hara's carrier bombers and attack planes attack Task Force 17 and damage both of Fletcher’s carriers. LEXINGTON is further damaged by gasoline vapors that ignite and trigger massive explosions. She has to be abandoned, then is scuttled by destroyer USS PHELPS (DD-360). The Battle of the Coral Sea halts the Japanese thrust toward Port Moresby and they cancel Operation MO.
15 May 1942:
Returns to Truk.
23 May 1942:
TOHO MARU arrives at Yokosuka.
27 May 1942:
Departs Yokosuka for Hashirajima.
29 May-5 June 1942: Operation “MI” – The Battle of Midway:
TOHO MARU departs Hashirajima with Captain Ota's Supply Group No. 1’s oilers NIPPON, KYOKUTO, KOKUYO and SHINKOKU MARUs with Nagumo's Carrier Striking Force's CarDivs 1, 2, Rear Admiral (later Vice Admiral) Abe Hiroaki's (39) Support Group's BatDiv 3/2's HARUNA, KIRISHIMA, CruDiv 8's TONE and CHIKUMA, Rear Admiral (later Vice Admiral) Kimura Susumu's (40) DesRon 10 light cruiser NAGARA with NOWAKI, ARASHIO, HAGIKAZE, MAIKAZE, KAZAGUMO, YUGUMO, MAKIGUMO, URAKAZE, ISOKAZE, TANIKAZE and HAMIKAZE.
15 June 1942:
Arrives at Kure.
17 June 1942:
TOHO MARU is assigned to Vice Admiral Hosogaya Boshiro's (36) Northern Force to support the Western Aleutians campaign and attached to Rear Admiral (Vice Admiral, posthumously) Kakuta Kakuji's (39) Second Carrier Striking Force.
25 June 1942:
Arrives at Yokosuka.
28 June 1942:
Departs Yokosuka.
30 June 1942:
Provides refueling support for a sortie from Ominato by Rear Admiral Kakuta's Second Carrier Striking Force that now consists of ZUIKAKU, RYUJO, JUNYO and ZUIHO. This force patrols S of Kiska until about 7 July.
10 July 1942:
TOHO MARU's assignment to the Northern Force is curtailed.
13 July 1942:
Arrives at Hiroshima Wan.
24 July 1942:
TOHO and SHOAN MARUs transit the Bungo Straits together.
7 August 1942: American Operation “Watchtower” – The Invasion of Guadalcanal, British Solomons:
Rear Admiral (later Admiral) Richmond K. Turner's (USNA ’08) Amphibious Task Force 62, covered by Vice Admiral (later Admiral) Frank J. Fletcher’s (USNA ’06) Task Force 61 and Rear Admiral (Admiral posthumously) John S. McCain's (USNA ’06) Task Force 63’s land-based aircraft, lands MajGen (later Gen/MOH/Commandant) Alexander A. Vandergrift’s 1st Marine Division on Florida, Tulagi, Gavutu, Tanambogo and Guadalcanal opening the campaign to retake the island.
14 August 1942:
Reassigned to the Guadalcanal Transport Replenishment No. 1 Group to support the Carrier Striking Force. Departs Yokosuka.
3 September 1942:
Arrives at Yokosuka.
7 September 1942:
Departs Yokosuka in convoy with tanker TOEI MARU bound for Truk. The ships sail at 15.5 knots.
4 October 1942:
Transits the Bungo Straits in a convoy also consisting of tanker NISSHO MARU and later that day arrives at Kure.
9 October 1942:
Departs Hiro.
E 16 October 1942:
N of the Solomons. TOHO MARU makes a rendezvous with the Supply Group’s oilers TOEI, KYOKUTO and KOKUYO MARUs to provide refueling for Nagumo's Third Fleet, Striking Force, CarDiv 1's SHOKAKU, ZUIKAKU and ZUIHO, CruDiv 7’s KUMANO and destroyers AMATSUKAZE, HATSUKAZE, TOKITSUKAZE, YUKIKAZE, ARASHI, MAIKAZE, TERUZUKI and HAMAKAZE.
17-24 October 1942:
N of the Solomons. Destroyer NOWAKI arrives from Shortlands. The Supply Force refuels the fleet at sea. The TOHO MARU is engaged in refueling operations for eight consecutive days. [3]
26 October 1942:
The Battle of Santa Cruz:
Nagumo's Carrier Strike Force engages Task Force 16's USS ENTERPRISE (CV-6) and Task Force 17's USS HORNET (CV-8) in an air battle. Nagumo's planes sink USS HORNET and damage USS SOUTH DAKOTA (BB-57) and USS SAN JUAN (CL-54).
30 October 1942:
Arrives at Truk.
6 November 1942:
Arrives at Kure.
15 November 1942:
Departs Hiro for Tarakan and Balikpapan. Joined by torpedo boat HATO off Sata Misaki and escorted to 31-55N, 132-15E.
26 November 1942:
An unknown captain assumes command. Captain Niimi is reassigned to the Yokosuka Naval District.
16 March 1943:
At 0800, arrives at Saipan from Truk.
17 March 1943:
At 1400, departs Saipan for Palau.
29 March 1943:
Macassar Strait, Celebes. At about 0400, LtCdr (later Rear Admiral) William S. Post’s (USNA ’30) USS GUDGEON (SS-211) attacks a convoy. In a night surface attack, Post fires six torpedoes and claims four hits on TOHO MARU. She sinks between Tarakan and Samarinda, Borneo at 00-30N, 118-26E. Casualties are unknown.
GUDGEON continues chasing the convoy. About noon that day, LtCdrPost attacks and damages oiler KYOEI MARU No. 2 at 00-54N, 119-01E.
1943:
Removed from the Navy List.
Authors' Note:
[1] In terms of appearance, all of Kawasaki's tankers were subtly different. It can be argued that TOHO MARU belonged in the same class as TATEKAWA and NIPPON MARUs. Her funnel casing was larger and her amidships derrick posts faced aft, not forward. On the other hand, some western merchant ship authorities grouped TOHO MARU with TOA and KYOKUTO MARUs. In western convention, it is appearance and not engine size that determines class.

[2] Hawaiian time.

[3] On 1 Nov '42, Captain Niimi visits classmate Vice Admiral (promoted that same day) Ugaki Matome (40)(former CO of HYUGA), Chief of Staff, Combined Fleet aboard flagship YAMATO at Truk. Niimi notes that TOHO MARU has refueled over 400 ships and transfered over 110,000-tons of fuel since the Hawaiian Operation.
Thanks goes to Allan Alsleben of Oregon and to Gilbert Casse of France for his contribution to revisions. Thanks also go to Robert MacArthur of CA.